Photocurable compositions have found wide use in many industrial and commercial applications such as in textiles, adhesive, sealants, paints and other coatings because they cure rapidly and do not contain volatile solvents to any large extent as well as having in many cases advantages in flow properties, pigment binding properties and gloss retention. Among the monomers used in the production of photocurable compositions are the hydroxyalkyl acrylate and hydroxyalkyl methacrylate esters, which are generally produced by the reaction of alkylene oxides with acrylic or methacrylic acid. This reaction is well known to those skilled in the art.
It is of great importance that by-product formation during the preparation of hydroxyalkyl acrylates and methacrylates from alkylene oxide and acrylic or methacrylic acid be minimized in order to avoid, to as great an extent as possible, polymerization problems during distillation of the crude products to isolate the refined material. In particular, the formation of the diacrylic and dimethacrylic esters of the alkylene glycols should be avoided due to the known poor stability of the diacrylates and dimethacrylates toward polymerization which is primarily responsible for instability of crude products. Undesirable by-product formation usually increases with temperature and residence time.
In order to increase the efficiency of this very useful reaction, those skilled in the art have sought catalysts which would promote the reaction at lower temperatures and shorter residence times in attempts to minimize by-product formation. Because of the economic importance of the reaction of alkylene oxides with carboxylic acids such as acrylic and methacrylic acid, there continues an intense search for novel compounds which can effectively and efficiently catalyze this reaction. Any such catalyst would be of great importance.